Whether a movie could be made of Cormac McCarthy’s Pulitzer Prize-winning novel The Road was once the subject of spirited debate. The story of a father and son braving the ruins of post-apocalyptic America has been called unfilmable, yet here is John Hillcoat’s reverent adaptation, faithful to the letter and the spirit, relentlessly bleak but with a sliver of hope for the future.

A decade has passed since some unnamed disaster left the earth infertile, its highways littered with abandoned cars, its buildings and bridges reduced to rubble. Roving gangs of cannibals and thieves roam the countryside where the man (Viggo Mortensen) and his son (Kodi Smit-McPhee) struggle through cold, unforgiving days, their worldly possessions packed in a shopping cart, their rations critically low.

The man has a revolver for protection, but also as an exit strategy: Its chamber holds two bullets, one for the boy and one for himself. Suicide in McCarthy’s dismal future is epidemic, and perhaps the sanest response to a world hardly capable of sustaining human life. (The man’s pregnant wife, played by Charlize Theron and seen only in harrowing flashbacks, certainly thinks so.) Yet the man refuses to give in, as she did. His son is reason enough to survive.

Their odyssey is a haunting one, never more so than when they stumble onto a den of cannibals and discover the flesh-eaters’ prey, naked and locked in a cellar like animals saved for the slaughter. This is a world where humanity is a luxury most can’t afford or have chosen to live without, but father and son cling to each other as they head south, in a desperate and likely futile attempt to get though the winter.

As you might have gathered, The Road is a grueling emotional ordeal, and Hillcoat (The Proposition), who shot the movie in the severe, muted tones McCarthy describes, never lets us forget it.

Yet through it all, father and son give us reason to imagine that all may not be lost. (The bearded Mortensen, wearing muddy rags, delivers a devastatingly tortured performance.) Their basic goodness, and the boy’s faith and innocence, suggest that decency can endure, albeit barely, in an otherwise barren world.

The Road may prove too grim for newcomers to McCarthy’s story, and too literal-minded a translation for those who know it well. I found the film moving, intelligently crafted and perfectly cast. The journey is exhausting, but in the man and his son we find spirits that refuse to be broken, even in a world God has forsaken.